1. Field of the Invention
The present invention relates to a mobile radio in a cellular wide range mobile communication system.
2. Description of the Prior Art
A mobile phone system comprises a mobile unit, a cell site, and a mobile telecommunication switching office (MTSO), and effects connections among different MTSOs and a connection with a general telephone set via general telephone line. In the mobile phone system, an automatic telephone exchange office is required to store the position of a mobile since it moves at all times. Therefore, when the mobile runs over a very wide area, the position is automatically registered from the mobile unit into the automatic telephone exchange office.
Thus, a tracking exchange function is necessary to track a position of the mobile unit. Such a tracking exchange function is disclosed, for example, in Z. C. Fluhr and P. T. Porter "Advanced Mobile Phone Service: Control Architecture" THE BELL SYSTEM TECHNICAL JOURNAL, Vol. 58, No. 1, January 1979, pp 43 to 69, and Iizuka et al "Mobile Phone starts to Run to a Commercial Base" Nikkei Electronics, June 26, 1978, pp 58 to 78 (in Japanese). Namely, the wide area mobile communication system includes in general many service areas, each of which usually has a mobile communication switching office. The present position of the mobile unit is stored in a home memory office (effected by MTSO) as a part of subscriber's information. With any call in to the mobile unit, a corresponding mobile communication switching office accesses to the home memory office and investigates the present position of the call-in mobile unit to control terminating connection to the corresponding area.
However, the wide area mobile communication system described above requires of the existing telephone exchange network to be modified for obtaining a tracking exchange function, and further it needs to provide position detection and position registration functions to itself. Thus, the prior wide area mobile communication system suffers from a problem of an increase in cost required for the system itself including the mobile unit.